Synthesis of BiOBr/WO3 p–n heterojunctions with enhanced visible light photocatalytic activity

Abstract

A prerequisite for the development of photocatalysis techniques is to obtain photocatalysts with remarkable activity. Herein, we have reported BiOBr/WO₃ p–n heterojunctions as novel and efficient visible-light-driven photocatalysts. The BiOBr/WO₃ p–n heterojunctions have been prepared through an electrospinning–calcination–solvothermal method, and they all present a flower-like superstructure. The photocatalytic activities of these p–n heterojunctions are investigated by degrading rhodamine B (RhB), methyl orange (MO) and para-chlorophenol (4-CP) under visible light irradiation (λ > 400 nm), respectively. When RhB serves as the target pollutant, all BiOBr/WO₃ p–n heterojunctions with different theoretical molar ratios of BiOBr and WO₃ (1/0.5, 1/1, 1/2) exhibit higher photocatalytic activity than pure WO₃ or BiOBr. Especially, the BiOBr/WO₃ p–n heterojunction with a molar ratio of 1/1 displays the highest photocatalytic activity among all the as-synthesized catalysts, even higher than the activity from the mixture of two individual photocatalysts with the same weight of components (WO₃ and BiOBr). In addition, when MO or 4-CP acts as the target pollutant, the BiOBr/WO₃ p–n heterojunction with a molar ratio of 1/1 still exhibits excellent photocatalytic performance. Furthermore, the recycling experiment confirms that the BiOBr/WO₃ p–n heterojunction is essentially stable during the photocatalytic process. The enhanced photocatalytic activity of the BiOBr/WO₃ p–n heterojunction is predominantly attributed to the efficient separation of photogenerated electrons and holes. The photogenerated holes (h⁺) and superoxide radical anions (˙O₂⁻) have been found to be the primary reactive species responsible for the nearly complete mineralization of RhB dye in water.